Spinal plates have been developed for stabilization of various portions of the spine after various surgical procedures, particularly spinal fusion procedures. Conventional spinal fixation plates typically take the form of a unitary plate with a pair of bone screw openings at opposing ends. The plate is placed over an excavated bone graft-receiving site in the vertebral column, in which a bone graft is located for fusion to adjacent vertebrae, and secured in place with bone screws. These prior art spinal fixation plates fix the adjacent vertebrae on opposite sides of the bone graft-receiving site a set distance relative to one another.
While the fixation plates discussed above are suitable for some situations, they also pose some difficulty in practice due to their lack of adjustability to a particular patient's needs. In particular, such fixation plates have a predetermined length with a predetermined spacing between the screw holes. As such, when a fixation plate with a different spacing is required for a particular patient, another fixation plate must be made available. As the particular needs of a patient may not be known prior to surgery, this necessarily means that multiple sizes of plates must be kept in ready inventory. In response to this, some forms of variable length fixation plates have been proposed, with varying degrees of success. The variable length devices allow the surgeon to adjust the length of the device during surgery, and then to fix that length via suitable locking mechanisms. However, even with variable length devices, the overall length of the device is fixed during surgery and does not change post-operatively.
It has been recognized that it may be beneficial to subject the bone graft to compression over time as the graft fuses to the vertebrae. Use of the conventional fixed length or variable length spinal plates discussed above generally precludes compression of the bone graft beyond any initial compression achieved during the surgical procedure. As such, there remains a need for additional approaches to spinal fixation, advantageously approaches that allow the bone graft to be progressively compressed between adjacent vertebrae over time.